Simultaneous enhancements of light-harvesting and charge transfer in UiO-67/CdS/rGO composites toward ofloxacin photo-degradation

Abstract

Antibiotics residues in aquatic environments has aroused great public concern since they cannot be effectively removed by conventional biological degradation. Sunlight-driven photo-degradation has been recognized as one of most efficient approach for the antibiotics removal. Herein, we proposed a novel strategy of simultaneous light-harvesting and electron-relay-penetration for the photocatalytic degradation of target antibiotics of ofloxacin (OFL). By incorporating visible-light responded semiconductor CdS nanoparticles into MOF and encapsulating by excellent conductor rGO thin sheets, a series of mesoporous composites of UiO-67/CdS/rGO-x were developed. As a result, the obtained UiO-67/CdS/rGO-1 showed the highest OFL degradation efficiency of 93.4% within 30 min for a 10 ppm OFL solution under the simulated sunlight, in which the turnover frequency (TOF) of 5.44 × 10−3 g(OFL) min−1 g(Cat.)−1 showed an order of magnitude increase over the relevant works. The mechanism study revealed the superoxide radicals O2− and photo-generated hole h+ were the excitons for the photocatalytic oxidation. The equalized Fermi level of UiO-67/CdS heterojunctions was formed to facilitate the electrons relaying, spilling-over, and penetrating through wrapped thin-layered rGO; meanwhile, the selective adsorption of OFL synergistically enhanced the photocatalysis, and hence provided a promising strategy for environmental remediation.